Tool assembly for surgical stapling device

ABSTRACT

A surgical stapling device including an independently rotatable tool assembly is disclosed. The tool assembly includes an anvil and a cartridge assembly which are movable in relation to each other between spaced and approximated positions. A clamp member is provided to maintain a proximal end of the cartridge assembly and anvil in juxtaposed alignment in the approximated position. A dynamic clamping member is provided to define a maximum tissue gap between the cartridge assembly and anvil during firing. A drive member including a flexible coaxial drive cable including a center rod and an outer sheath is connected to the clamp member and dynamic clamping member to move the member between first and second positions.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a National Stage Application of PCT/US03/31652 under 35 USC§371(a), which claims priority of U.S. Provisional Patent ApplicationSer. No. 60/416,088 filed Oct. 4, 2002, entitled “Surgical StaplingDevice”, now abandoned, the disclosures of which are hereby incorporatedby reference in their entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a tool assembly for treating tissue.More particularly, the present disclosure relates to an endoscopicsurgical tool assembly capable of articulation and rotation for treatingtissue.

2. Background of Related Art

Surgical staplers for clamping tissue between opposed jaw structures ofa tool assembly and thereafter fastening the clamped tissue are wellknown in the art. These devices may include a knife for incising thefastened tissue. Such staplers having laparoscopic or endoscopicconfigurations are also well known in the art. Examples of theseendoscopic surgical staplers are described in U.S. Pat. Nos. 6,330,965,6,250,532, 6,241,139, 6,109,500 and 6,079,606, all of which areincorporated herein by reference in their entirety.

Typically, these staplers include a tool member having a staplecartridge for housing a plurality of staples arranged in at least twolaterally spaced rows and an anvil which includes a plurality of stapleforming pockets for receiving and forming staple legs of the staples asthe staples are driven from the cartridge. The anvil, typically, ispivotally supported adjacent the cartridge and is pivotable between openand closed positions.

During laparoscopic or endoscopic surgical procedures, access to asurgical site is achieved through a small incision or through a narrowcannula inserted through a small entrance wound in a patient. Because oflimited area to access the surgical site, many endoscopic staplersinclude mechanisms for rotating the endoscopic body portion of thedevice or articulating the tool assembly of the device. Typically, eachmechanism is controlled by an actuator which has to be manipulated by asurgeon to properly orient the tool assembly in relation to tissue to betreated. Such manipulations are time consuming and may not result in theexact orientation of the tool assembly desired by the surgeon.

Accordingly, a need exists for an improved endoscopic surgical staplingdevice which includes a mechanism for adjusting the orientation of atool assembly which is easy to operate and is capable of positioning atool assembly at any desired orientation.

SUMMARY

In accordance with the present disclosure, a surgical instrumentincluding a tool assembly having a pair of jaws is disclosed. The toolassembly includes an anvil and a cartridge assembly which has aplurality of fasteners supported therein. The cartridge assembly ismovable in relation to the anvil between a spaced position and anapproximated position. A clamp member is movable from a retractedposition to an advanced position to move the cartridge assembly inrelation to the anvil from the spaced position to the approximatedposition. A dynamic clamping member is movably positioned in relation tothe anvil and cartridge assembly from a retracted to an advancedposition to eject the plurality of fasteners from the cartridgeassembly. A drive member formed from a flexible cable is operablyconnected to the clamp member and the dynamic clamping member and ismovable to move the clamp member and the dynamic clamping member betweentheir retracted and advanced positions.

Preferably, the drive member includes a coaxial cable including an outersheath and a center rod. The center rod is axially movable and rotatablein relation to the outer sheath. The outer sheath is operably connectedto the clamp member and the center rod is operably connected to theclosure member.

Preferably, a collar is pivotally secured to a body portion of astapling device. The body portion may form the distal end of a surgicalstapling device or the proximal end of a disposable loading unit.

Preferably, the tool assembly is rotatably mounted to the collar member.In a preferred embodiment, the center rod of the coaxial cable isconnected to the dynamic clamping device such that rotation of thecenter rod effects rotation of the closure member to effect rotation ofthe tool assembly in relation to the collar member to facilitateindependent rotation of the tool assembly.

In a preferred embodiment, the dynamic clamping member includes a firstflange portion positioned to engage a surface of the anvil and a secondflange portion positioned to engage a surface of the cartridge assembly.The first and second flange portions together define a maximum tissuegap between the anvil and cartridge assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Various preferred embodiments of the presently disclosed surgicalstapling device are disclosed herein with reference to the drawings,wherein:

FIG. 1 is a side perspective view of one preferred embodiment of thepresently disclosed surgical stapling device with the anvil andcartridge assembly in the spaced position;

FIG. 1A is a side perspective view of the proximal end of the anvil, therotation collar and the adaptor of the surgical stapling device shown inFIG. 1;

FIG. 2 is a side view of the surgical stapling device shown in FIG. 1;

FIG. 3 is a top view with the internal components in phantom of thesurgical stapling device shown in FIG. 2;

FIG. 4 is a cross-sectional view of the surgical stapling device shownin FIG. 2 taken along a longitudinal axis of the device through thecartridge assembly;

FIG. 5 is a cross-sectional view of the surgical stapling device shownin FIG. 3 taken along a transverse axis through the dynamic clampingmember with the tool member approximated;

FIG. 6 is a cross-sectional view of the surgical stapling device shownin FIG. 3 taken along a transverse axis of the tool assembly through thecartridge assembly and anvil;

FIG. 7 is a top perspective view of the dynamic clamping member of thesurgical stapling device shown in FIG. 1;

FIG. 8 is a top perspective view of the clamp member of the surgicalstapling device shown in FIG. 1;

FIG. 9 is a top perspective view of the drive collar of the surgicalstapling device shown in FIG. 1;

FIG. 10 is a side perspective exploded view of the tool assembly of thesurgical stapling device shown in FIG. 1;

FIG. 11 is an enlarged view of the proximal end of the tool assemblyshown in FIG. 10;

FIG. 12 is a side perspective exploded view of the endoscopic bodyportion of the surgical stapling device shown in FIG. 1;

FIG. 13 is a side cross-sectional view of the surgical stapling deviceshown in FIG. 1;

FIG. 14 is another embodiment of the closure member according to thepresent disclosure;

FIG. 15 is a top plan view of the cartridge housing of the presentdisclosure;

FIGS. 16A and 16B are perspective views of the sled and pusher membersof the present disclosure;

FIG. 17A is a cross-sectional end view of a portion of the cartridgeassembly of FIG. 16B, taken along lines 17A, illustrating thearrangement of the sled, pusher member, and staple according to anembodiment of the present disclosure; and

FIG. 17B is a cross-sectional end view of a portion of the cartridgeassembly illustrating the arrangement of the sled, pusher member, andstaple according to another embodiment of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the presently disclosed surgical staplingdevice will now be described in detail with reference to the drawings inwhich like reference numerals designate identical or correspondingelements in each of the several views.

FIGS. 1-13 illustrate one preferred embodiment of the presentlydisclosed surgical stapling device shown generally as 10. Staplingdevice 10 includes a tool assembly 12 having an anvil 14 and a cartridgeassembly 16, an endoscopic body portion 18, a clamp member 20, and arotation collar 22. Tool assembly 12 is pivotally supported at thedistal end of endoscopic body portion 18 about a pivot member 24. Anadaptor 26 is secured to the distal end of body portion 18 and includesupper and lower extensions 28. A spacer 18 a (FIG. 12) may be positionedwithin body anterior 8 to maintain the positioning of the internalcomponents of the device. Alternately, adaptor 26 can be monolithicallyformed with endoscopic body portion 18. Pivot member 24 extends betweenupper and lower extensions 28 and a proximal portion 22 a (FIG. 1A) ofrotation collar 22 such that tool assembly 12 can articulate in relationto the longitudinal axis of endoscopic portion 18 approximately 90°. Itis envisioned that a variety of different articulation joint types, e.g,ball and socket, flexible coupling, universal joint etc., may beprovided to allow for greater degrees of articulation.

Cartridge assembly 16 includes a cartridge 16 a housing a plurality ofstaples (not shown), a channel portion 30 defining a recess forreceiving cartridge 16 a, a dynamic clamping member 32 (FIG. 7), and asled 31. Dynamic clamping member 32 preferably is positioned proximallyof the sled 31 within cartridge 16 a. A knife blade 34 is preferablypositioned on an intermediate, preferably central, body portion 32 a ofdynamic clamping member 32 to incise fastened tissue. The knife blade 34may be machined directly into the dynamic clamping member or may befixedly or removably secured thereto. Alternately, knife blade 34 may beformed on or fixedly, removably or pivotally secured to the sled. Sled31 is slidably positioned to translate through cartridge 16 a to ejectstaples from the cartridge in a known manner. Dynamic clamping member 32includes upper and lower flanges 36 a and 36 b. As shown in FIG. 5,flange 36 a is positioned within a slot or recess 38 formed in cartridge16 a and flange 36 b is positioned within a recess 40 formed in anvil14. Alternately, flanges 36 a and 36 b need not be slidably positionedin recesses but rather need only engage an upper bearing surface onanvil 14 and a lower bearing surface on cartridge assembly 16. Asillustrated in FIG. 7, flanges 36 a and 36 b preferably are arcuate orsemi-circular to minimize deflection and maintain alignment of the anviland/or cartridge during actuation of the stapler. Dynamic clampingmember 32 is positioned proximally of the sled in engagement therewithand is translatable through the cartridge. Dynamic clamping member 32provides, restores and/or maintains a desired, preferably uniform,tissue gap in the area of tool assembly 12 adjacent sled 31 duringfiring of device 10. Movement of dynamic clamping member 32 throughcartridge assembly 16 advances the sled through the cartridge assembly.

It is envisioned that the anvil and/or dynamic clamping member,preferably both, be formed of a material and be of such a thickness orgauge to minimize deflection of the respective anvil and/or dynamicclamping member during clamping, translation through, and firing of thedevice. Such materials include surgical grade stainless steel.Preferably, the anvil is formed as a solid one piece unit. Alternately,as known in the art, the anvil may be formed of an assembly of partsincluding an anvil body and anvil plate having a plurality of stapleforming pockets. It is desired that the anvil be as strong as reasonablypossible and necessary to minimize distortion, e.g., the distal end ofthe anvil bowing upwardly during clamping or preclamping and/or duringstaple firing.

Referring to FIG. 1A, the proximal end of anvil 14 includes acylindrical portion 14 a having an annular recess 14 b. Cylindricalportion 14 a is dimensioned to be received within bore 22 a of collar22. At least one pivot pin 23 (FIG. 1) extends through collar 22 intorecess 14 b to axially fix the proximal end of anvil 14 within bore 22a. Since pin 23 is positioned within annular recess 14 b, anvil 14 isrotatable within collar 22. It is envisioned that other means may beprovided to rotatably attach anvil 14 to collar 22. A second pin 25(FIG. 1) extends through collar 22 to secure collar 22 to a distal endof articulation link 52 as will be described below.

Although not shown, in a known manner the proximal end of channelportion 30 of cartridge assembly 16 includes a recess for receiving apivot member, e.g., a tab or pin, formed on or attached to the proximalend of anvil 14. The proximal ends of anvil 14 and cartridge 16 areconfined within collar 22 to prevent the pivot member of the anvil frombecoming disengaged from the recess in channel portion 30 of cartridgeassembly 16. Alternately, other mechanical arrangements known in the artmay be used to pivotally secure anvil 14 to cartridge assembly 16. It isnoted that since cartridge assembly 16 is pivotably attached to anvil14, both are rotatable in relation to collar 22.

Referring to FIGS. 1 and 4, an articulation mechanism is provided toarticulate tool assembly 12 in relation to endoscopic body portion 18.The articulation mechanism includes a proximal articulation link 50 anda distal articulation link 52. Proximal articulation link 50 has a firstend 50 a extending from the proximal end of endoscopic body portion 18and a second end 50 b positioned within body portion 18 and pivotallyconnected to a first end 52 a of second articulation link 52. A secondend 52 b of articulation link 52 is pivotally connected to rotationcollar 22 by pin 25 (FIG. 1) at a point offset from pivot member 24,i.e., the pivot axis of tool assembly 12. Articulation link 52 isconfined in a slot 54 formed in endoscopic body portion 18. Because ofthe confinement, the articulation mechanism is only capable ofarticulating tool assembly 12 over an arc on one side of thelongitudinal axis of the device. Preferably, each of the pivotalconnections identified above includes a pivot pin. Alternately, pivotmembers may be integrally formed with the above components or pivotmembers not including pins may be used. Other types of articulationlinks are also comtemplated.

In use, when the longitudinal axis of tool assembly 12 is aligned withthe longitudinal axis of body portion 18 and proximal articulation link50 is retracted in the direction indicated by arrow “A” in FIG. 4, link50 retracts link 52 to effect articulation of tool assembly 12 aboutpivot member 24 in the direction indicated by arrow “B” in FIG. 4. Toolassembly 12 can be returned to a non-articulated position by advancinglink 50 in the direction indicated by arrow “C”. The mechanism forcontrolling movement of articulation mechanism will be discussed below.

Referring to FIGS. 3-9, a drive mechanism for approximating anvil 14 andcartridge assembly 16, firing the staples, and rotating tool assembly 12in relation to collar 22 is provided. The drive mechanism includes acoaxial cable or drive member 60 (FIG. 3) having a center rod 62 and anouter sheath 64, a drive collar 66 (FIG. 9), a clamp member, here shownas clamp ring 20, and dynamic clamping member 32. Center rod 62 is orincludes a flexible member having a suitable compression strength forpushing dynamic clamping member 32 through cartridge 16 a. Preferably,center rod 62 includes a left or right hand wound flexible cable.Alternately, other materials having suitable strength characteristicsmay also be used, e.g., Nitinol™. The diameter of center rod 62 must besmall enough to be positioned within available space within cartridge 16a. Outer sheath 64 is positioned about center rod 62 and in partfunctions to stabilize and prevent buckling of center rod 62 while it isin compression. Preferably, outer sheath 62 is also a flexible cableformed from a steel mesh, reinforced plastic or a nickel titanium alloysuch as Nitinol™. It is also envisioned that other suitable materialshaving the requisite strength requirements including a polypara-phenyleneterephthalamide material such as Kevlar™ commerciallyavailable from DuPont, may be used to form the outer sheath.

Center rod 62 is slidably positioned within outer sheath 64 and includesa first proximal end 62 a (FIG. 4) preferably extending from theproximal end of endoscopic body portion 18 and a second end 62 battached to dynamic clamping member 32. Dynamic clamping member 32preferably includes a recess 68 (FIG. 7) formed therein for receivingsecond end 62 b of center rod 62. Second end 62 b can be secured todynamic clamping member 32 by crimping, welding as in FIG. 4, brazing,pins, etc. within or utilizing for example recess 68 and, may also bemachined to conform to the shape of recess 68.

Outer sheath 64 has a first proximal end 64 a extending preferably fromthe proximal end of elongated body portion 18 and a second distal end 64b fixedly connected to drive collar 66. Drive collar 66 (FIG. 9)preferably includes a central bore 70 for receiving outer sheath 64 andproviding a channel for passage of center rod 62 therethrough. The outersurface of drive collar 66 preferably includes engagement structure,e.g., notches 72, for engaging clamp member or ring 20 in a rotatablyfixed relation. Clamp ring 20 also includes engagement structure, e.g.,veins or projections 74, for mating with the engagement structure ofdrive collar 66 to rotatably secure drive collar 66 to clamp ring 20 sothat they will rotate together. The distal end 20 a of clamp ring 20includes a pair of cutouts 76 configured to receive and engage flangeportions 36 a and 36 b of dynamic clamping member 32.

In use, center rod 62 and outer sheath 64 are movable together from aretracted position to a partially advanced position to advance drivecollar 66, clamp ring 20 and dynamic clamping member 32 to a firstadvanced position. Clamp ring 20, preferably, is positioned about theproximal end of anvil 14 and cartridge assembly 16. Cartridge assembly16 includes a cam surface 80 (FIG. 2) formed on an external surfacethereof. As dynamic clamping member 32 moves from the retracted positionto the first advanced position, flange 36 b of dynamic clamping member32 engages cam surface 80 of cartridge assembly 16 to pivot cartridgeassembly 16 from the open position to the closed or clamped position.Clamp ring 20 is also moved distally from the first advanced position toa position encircling the proximal portions of anvil 14 and cartridgeassembly 16. In this position, clamp ring 20 prevents the gap betweenproximal portions of anvil 14 and cartridge assembly 16 from exceeding apredetermined distance.

After center rod 62 and outer sheath 64 have been moved to the firstadvanced position to move cartridge assembly 16 and, accordingly, anvil14 to the clamped position, center rod 62 can be advanced independentlyof outer sheath 64 to a second advanced position to move dynamicclamping member 32 through cartridge 16 a to eject staples from thecartridge assembly and cut tissue by use of knife blade 34 of closuremember 32. It is contemplated that, alternately, flanges 36 a and 36 bof closure member 32 could engage a cam surface on anvil 14 and/orcartridge assembly 16 to pivot one or both to provide clamping oftissue. Referring to FIGS. 5 and 6, a channel 82 is formed in cartridge16 a to provide lateral support to center rod 62 to prevent center rod62 from buckling during movement of center rod 62 from the retractedposition to the second advanced position.

As discussed above, anvil 14 is rotatably secured to collar 22, centerrod 62 is fixedly attached to dynamic clamping member 32, and outersheath 64 is fixedly attached to drive collar 66. When coaxial member 60is rotated, the entire tool assembly rotates about the central axis ofcollar 22. More specifically, since dynamic clamping member 32 isconfined within anvil 14 and cartridge assembly 16, any torque appliedto center rod 62 is transferred via dynamic clamping member 32 to toolassembly 12. Thus coaxial member 60 can be rotated to rotate toolassembly 12 about the longitudinal axis of collar 22.

The above-described tool assembly may be, modified to be, or may beincorporated into a disposable loading unit such as disclosed in U.S.Pat. No. 6,330,965 or attached directly to the distal end of any knownsurgical stapling device. Although a handle assembly for actuating thearticulation member and the approximation or clamping, firing, and toolrotation mechanisms have not been specifically disclosed herein, it isto be understood that the use of a broad variety of different actuatingmechanisms and handle configurations are envisioned including toggles,rotatable and slidable knobs, pivotable levers or triggers, pistolgrips, in-line handles, remotely operated systems and any combinationthereof. For example, as shown in FIG. 13A, the handle assembly mayinclude a pistol-type 200 including a tool assembly rotation knob 210,an articulation lever 212 and a body rotation knob 214. The use of anabove-described tool assembly as part of a robotic system is alsoenvisioned.

It is envisioned that utilization of a heavier gauge material for theanvil assembly alone, and preferably also for the closure member and theclamping ring provides an enhanced clamping pressure along the length ofthe tissue which, in turn, provides a more uniform tissue gap betweenthe respective anvil and cartridge surfaces adjacent to and ahead ofwhere the staples are formed through tissue. Moreover, utilizing theclamping ring for pre-clamping the tissue, i.e., clamping the tissueprior to deformation of the staples, tends to force some tissue fluiddistally and radially outwardly which reduces the likelihood ofhydraulically displacing of the staples during their deformation. Use ofa closure member or the like which clamps as it translates along thetool member helps to compensate for the fluid flow and/or from withinthe tissue and/or bowing out of the distal end of the anvil and therebymaintain the desired tissue gap between the anvil and the cartridgeassembly.

In another preferred embodiment as shown in FIG. 14, closure member 132includes upper and lower flanges 136 a, 136 b spaced apart and attachedto an intermediate portion 132 a. As in the previous embodiment, closuremember 132 is preferably positioned proximally of the sled 140 partiallywithin a cartridge 118 of cartridge assembly 116. A knife blade 134 ispreferably positioned on intermediate portion 132 a of closure member132 for incising fastened tissue. Knife blade 134 may be machineddirectly on a section of intermediate portion 132 a or it may be fixedlyor removably attached to intermediate portion 132 a. Alternatively,knife blade 134 may be formed as part of sled 140 or may be fixedly orremovably secured to sled 140. Upper and lower flanges 136 a, 136 b aregenerally arcuate structures with substantially identical curvatures.Alternately, the curvature of the upper and lower flanges 136 a, 136 bmay differ to provide greater or lesser structure support. Each flange136 a, 136 b further includes an inner surface 135 a, 135 b and an outersurface 137 a, 137 b. Preferably, closure member 132 is constructed sothat the inner surfaces 135 a, 135 b are facing each other. Upper andlower flanges 136 a, 136 b function to define the maximum tissue gapbetween anvil and cartridge surfaces.

In one preferred embodiment, cartridge assembly 116 includes a pluralityof retention slots 122 arranged along a longitudinal axis of cartridgehousing 118. As shown in FIG. 15, retention slots 122 are arranged toform first and second groups 124, 126. Preferably, each group 124, 126includes three rows of retention slots 122 configured such that at leastone of the rows is longitudinally offset from the remaining rows. It isfurther preferred that at least two rows of retention slots 122 aredisposed in each group 124, 126 of cartridge assembly 118 such that eachretention slot 122 of an inner row is in substantial longitudinalalignment with a corresponding retention slot 122 in the outer row andthe intermediate row of retention slots 122 is longitudinally offsetfrom the inner and outer rows. Thusly, the inner and outer rows ofretention slots 122 are longitudinally aligned from the most proximallocation to the most distal location of cartridge housing 118.Preferably, a retention slot 122 in the inner and outer rows define theproximal-most and distal-most retention slot. The advantageouspositioning of the retention slots 122 as described improves thefastening of tissue and minimizes bleeding.

Referring to FIGS. 16A-17B, additional embodiments of sled 140 andpusher member 150 are illustrated. Pusher member 150 includes a baseportion 152. In FIG. 16A, sled 140 has been advanced longitudinally incartridge housing 118 and begins to engage base 152 of pusher member150. As sled 140 is further advanced in a longitudinal direction (FIG.16B), base 152 of pusher member 150 engages upstanding cam wedges 144 ofsled 140. Longitudinal movement of sled 140 transfers the longitudinalmotive forces along cam wedges 144 and thereby to pusher members 150.Preferably, pusher members 150 are in a fixed relationship to thelongitudinal movement of sled 140 and move substantially orthogonal tothe longitudinal axis of cartridge assembly 118, thereby transferringthe motive forces to backspan 162 of staple 160 for moving staple 160through retention slot 122. In one preferred embodiment, as illustratedin FIG. 17A, cam wedges 144 of sled 140 engage a recess 154 in pushermember 122. Recess 154 is configured and adapted for sliding engagementof cam wedge 144. Once cam wedge 144 engages recess 154, furtherlongitudinal movement of sled 140 acts to maintain pusher member 150 insubstantial vertical alignment to the longitudinal axis. Thuslyconfigured, once engaged by sled 140, pusher member 150 maintains itssubstantially orthogonal relationship to the longitudinal axis as itmoves through retention slot 122. Alternatively, pusher member 150 a maybe configured to reside with a-space 146 a between cam wedges 144 a ofsled 140 a as shown in FIG. 17B. As in the previous embodiment, base 152a of pusher member 150 a is configured and adapted for slidingengagement with space 146 a of sled 140 a. Further still, as pushermember 150 a engages cam wedge 144 a of sled 140 a, pusher member 150 amaintains its substantially orthogonal relationship to the longitudinalaxis as it moves through retention slot 122.

It will be understood that various modifications may be made to theembodiments disclosed herein. For example, although the tool assembly isdescribed exclusively as a stapling device, it may be used to applyfasteners other than staples including two-part fasteners. Therefore,the above description should not be construed as limiting, but merely asexemplifications of preferred embodiments. Those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. A tool assembly for use with a surgical stapler comprising: an anvil;a cartridge assembly having at least one staple, the cartridge assemblybeing movable in relation to the anvil between spaced and approximatedpositions; a clamp member positioned adjacent a proximal end of the toolassembly, the clamp member being movable from a retracted position to anadvanced position and being configured to maintain a proximal end of theanvil and cartridge assembly in the approximated position when the clampmember is in the advanced position; and a dynamic clamping memberpositioned within the tool assembly and movable from a retractedposition through the tool assembly to an advanced position to ejectstaples from the cartridge assembly, the dynamic clamping memberincluding an upper flange portion engaging a surface of the anvil and alower flange portion engaging a surface of the cartridge assembly, atleast one of the upper and lower flange portions having an arcuatecross-section along an axis transverse to a longitudinal axis of thecartridge assembly to define an arcuate surface positioned to engage atleast one of the surface of the anvil and the surface of the cartridgeassembly, the dynamic clamping member being configured to define amaximum tissue gap between the anvil and the cartridge assembly duringejection of staples from the cartridge assembly.
 2. A tool assemblyaccording to claim 1, further including a knife blade associated withthe dynamic clamping member.
 3. A tool assembly according to claim 2,wherein the knife blade is formed on a central body portion of thedynamic clamping member.
 4. A tool assembly according to claim 3,wherein the cartridge assembly includes a sled and at least one pusherassociated with each of the at least one staple, the sled being drivenby the dynamic clamping member into engagement with each pusher toadvance each pusher and eject the staple from the cartridge assembly. 5.A tool assembly according to claim 4, wherein the cartridge assemblyincludes a plurality of staples and pushers.
 6. A tool assemblyaccording to claim 5, wherein the upper flange and lower flange aresubstantially vertically aligned.
 7. A tool assembly according to claim6, wherein the knife blade is disposed on the central body portionbetween the upper and lower flanges.